A robot must recognize a current location of itself in order to automatically travel to a destination after defining a path to that destination.
An artificial marking scheme is generally used as a way of determining a location of robot. In the artificial marking scheme, artificial marks are used which are designed to be distinguished from a background. Such artificial marks are installed throughout an indoor place, and a robot finds the artificial marks to recognize the location of robot by obtaining images of artificial marks through photographing the artificial marks using a camera and processing the obtained images. The location of robot is calculated by referring the image coordinate of detected artificial mark and the indoor space coordinate of the artificial mark that is pre-stored in the robot. There were various methods of calculating the location of robot introduced.
The artificial marks are generally geometrical patterns such as a circle or a rectangle. In order to accurately recognize the current location of robot, the robot has to process images to recognize such a geometrical pattern. Since the image signal captured from the indoor space through the camera is seriously influenced by a direction of a light and a distance from the light to the camera, it is very difficult to stably recognize the artificial marks in the indoor space. Therefore, complicated calculating steps are required to improve the performance of recognizing the artificial marks in a general environment. However, the complicated calculating steps also increase the time of processing the image to recognize the location of robot. Therefore, it is impossible to calculate the location of robot in real time. Especially, it is almost impossible to recognize the location of robot at night since a camera barely captures images when there is not much light provided.
In order to overcome such a drawback, there was another conventional artificial marking scheme introduced, which uses a light source as the artificial marks that can be turned on and off. Such a conventional artificial marking scheme uses the light sources that emit a predetermined wavelength of light as the artificial marks. In order to capture the light sources, a camera having a filter passing the predetermined wavelength of light is used. Accordingly, an image processing is simplified and the reliability for recognizing the artificial marks is improved. Such a conventional artificial marking scheme is barely influenced by the light, and it can be used at the night to move the robot.
However, the light source artificial marks have no differences in their forms, generally. Therefore, it is difficult to distinguish one from another. That is, the artificial marks are turned on and off in sequence to recognize each of the artificial marks. Such a recognition procedure requires a time in proportion to the number of light sources. Also, the robot must be stopped before performing the light source recognition procedure. Therefore, the location of robot cannot be calculated in real time, and it cannot be used while the robot is moving.
A robot must be capable of changing a traveling path to a destination in order to implement the robot in an indoor space. It is because there are many dynamic obstacles existed such as human. In order to avoid collusion with these obstacles while the robot travels to the destination, the robot must frequently change its path to the destination. In order to establish the new path, the robot must recognize the current location of itself. If the robot must be stopped and the light source artificial marks are turned on and off in sequence for calculating the current location, it is very ineffective to manage and to drive the robot.